Electrical resistance element and alloy therefor



Patented June 2, 1936 .ELECTRICAL RESISTANCE ELEMENT AND 'ALLOY THEREFOR James L. Thomas, Garrett Park, Md., assignor to the Government or the United States, as represented by the Secretary of Commerce No Drawing. Original application November 22,

1934, Serial No. 754,310. Divided and this application November 18, 1935, Serial No. 50,378

3 Claims.

(Granted under the act of March 3, 1883, as

mended April 30,

The invention described herein may. bemanufactured and used by or'fortheGovernment of the United States for governmental purposes only without the payment of any royalty thereon.

This invention relates to anew and improved electrical resistance element, and is a division of my 4application Serial No. 754,310, filed Nov. 22nd, 193

Generally, in electrical measuring apparatus, coils of wire are utilized and difllculty has always beenencountered in obtaining a wire whose resistance remains stable or substantially constant. It is known that resistance changes with age and also with ordinary changes in laboratoryrtemperature. The change which takes place with age may be due to chemical action of the air upon the surface of the wire, or to changes in the crystal arrangement therein.

Further,'besides the stability, resistance alloys have included a number of different alloys composed of gold with the addition of approximately from 1.5 to 5 percent of chromium by weight. As

a result of the tests I have found the most dechromium and theremainder gold- Moreover, I have discovered that the addition of 1.5 to 5 percent of chromium to gold produces alloys having very small temperature coemcients of electrical resistance and that the temperature coefficient of the alloys depends upon the proportions of the two ingredients. f a

The first difllculty encountered was to discover a method by which the two ingredientscould be should have low temperature coefilcientsof re-. sistancein order that they maybe readily measof chromium. Specifically, my research and tests sirable mixture is approximately 2.1 percent of properly alloyed, and this method is described and claimed in my co-pending application, to which reference has been made above.

The following table is illustrative of the temperature-resistance' changes, of a 10-ohm coil of the 2.1 percent chromium alloy baked, at a temperature of 200 C. to bring its value to zero:

. The resistance of thiscoil was substantially independent of temperature throughout the entire I interval 20-30 C. With manganin a minimum variation of about 10 parts per million would have been expected in this entire temperature interval, which is nearly a hundred times that of the 2.1 percent chromium alloy. In testing 10-ohm and IOU-ohm coils the temperature resistance curves werefound to be substantially identical in each case. b

When manganin is used, in the construction of resistance standards, the coils are usually kept for a year or more in order to reach a reasonably stable state, but with my alloy this ageing is not necessary, and, obviously, is greatly preferable to the manganin. e

As will be evident to those skilled in the art, my invention permits of changes in percentages of elements in the alloy without departing from the spirit thereof or the scope of the appended claims,

What I claim is:

1. An electrical resistance element composed of an alloy comprised of gold and chromium, the chromium being in the'percentage of from one to five percent and the gold constituting the remainder of the element.

2. An alloy comprising 2.1" percent of chromium and the remainder gold.

3. An alloy'composed of gold and chromium, the chromium being in the percentage of from one to five per cent and the gold constituting the remainder.

' JAMES L. THOMAS. 

